Fungus populations of the genus Cercospora which cause diseases of celery, peanuts, sugar beets and bananas; of the genus Botrytis which cause diseases of grapes, tomatoes, lettuce and strawberries; and of the family Erysiphaceae which attack numerous plants occasionally contain minor segments of particular genetic types (strains) which respond to chemicals differently than the major portion of the population. Under common protective regimens, the major portion of the fungus population is controlled but one or more variant strains survive and, in the absence of competition from their kind, become damaging. Once such a situation has developed, it has been frequent practice to search for another fungicide that can be introduced to control the emerged strain. This invention provides mixtures of fungicides that provide control of the normally susceptible fungi without permitting the emergence to a damaging level of resistant fungus strains that are present.
The use of the individual elements of the composition of this invention are known. Loux U.S. Pat. No. 3,010,968 discloses many benzimidazolecarbamates but does not teach or suggest the use of methyl 2-benzimidazolecarbamate (MBC) as a foliar fungicide. The use of MBC as a foliar fungicide was first taught in Klopping, U.S. Pat. No. 3,657,443. The fungicidal use of tetramethylthiuramdisulfide, tetraethylthiuramdisulfide and zinc dimethyldithiocarbamate is taught in Donald E. H. Frear, Chemistry of the Pesticides, D. Van Nostrand Co., Third Ed., 1955, pages 294-300. However, there has been no suggestion of the uses of combinations of these fungicides to prevent emergence of tolerant strains within populations of normally susceptible fungi.